In order to maximize production of a given drilling operation, it is first necessary to determine whether a given region passed through during the drilling process has a high quantity of oil and/or gas contained therein. This region is termed the "formation of interest." Secondly, it is necessary to efficiently extract the oil and/or gas therefrom. One problem that is incurred in efficiently extracting oil and/or gas from a well that is determined to be productive is the mixing of salt water with the oil and/or gas. The presence of high levels of salt water in the formation requires additional steps for removal thereof in addition to the increased energy requirements to pump the water.
To determine the potential of a given well, a core sample is normally taken from the formation of interest. This extracted core is analyzed to determine various properties thereof such as porosity, permeability and oil saturation. From these properties, a determination can be made as to whether this particular region will produce a sufficient amount of oil and/or gas to warrant a pumping operation. If the determination is made that the well has a high probability of being productive, a well casing is then lowered into the well to provide a conduit for retracting fluids therefrom. After the well casing has been lowered, a special device is lowered into the well that carries an explosive charge for selected perforation of the casing. This apparatus is lowered to a predetermined depth and then discharged to perforate the well casing at that depth resulting in perforations along a selected segment that are spaced in predetermined depth increments. If pressure in the formation is of sufficient magnitude, the oil and/or gas will flow freely to the surface for extraction thereof. However, if this pressure is not sufficient, a pump must be installed for extraction purposes.
The first problem of determining whether the formation of interest will have a high production rate is to determine the amount of oil present in each foot-acre. This determination has been simplified with sponge coring techniques disclosed in U.S. Pat. No. 4,312,414, issued to Arthur Park, one of the present Applicants. Sponge coring enables a drilling company to determine a more accurate profile of the characteristics of a given core sample along its longitudinal axis at the various depths and the amount of oil contained within the pore space of the sample core. From this information, conventional techniques are then applied to determining where the perforations are to be placed. It is quite important to place these perforations at the correct points along the formation of interest in order to maximize the production. Although oil and/or gas may be contained in a given region, the flow of oil from this point may be impeded due to undesirable characteristics of a formation, and the undesirable characteristics may exist at certain portions of a given region.
In order to maximize production levels, there exists a need for an improved method of determining the predicted productivity of a potential well and placing the perforations in the well casing as a function of the data derived from present day coring techniques such as sponge coring.